This invention relates to a method for producing structures having a densified layer on the outer surface of a porous material.
Numerous methods for producing lightweight, load-bearing structural components for such applications as airframe components and construction materials have been proposed. For example, lightweight structural components have been fabricated using a "sandwich" construction in which facesheets are bonded to a porous core. Although this arrangement increases the bending and buckling section properties, there are a number of disadvantages: 1) the bonded joints between the core and the facesheets are often inconsistent, reducing reliability and causing overdesign which limits weight efficiency, 2) fabrication costs are high due to complex forming, core cutting, assembly, and joining steps, and 3) production of thin sections are unfeasible due to fabrication difficulties.
As disclosed in U.S. Pat No. 4,659,546, the disclosure of which is hereby incorporated by reference, porous material bodies used for load-bearing applications often employ trapped gas to create discrete internal porosity and reduce the overall density of the body. Since they contain sufficient shear strength to support solid facesheets under bending loads, such porous materials are often used as the core for sandwich construction of lightweight components.
There is a need in the art for an in-situ method of producing lightweight, non-sandwich structural components from porous materials having gas-containing voids.